In general, it may be said that up to that time three-fourths of the population of Illinois came from south of the Mason and Dixon line, with Kentucky making the largest single contribution, although a small foreign element was already arriving, mainly from the British Isles.
At the date of Statehood in 1818, Illinois may be said to have been dominated by the Ulster Scots who had come in from the southern Piedmont. These represented, on the whole, a class which for lack of wealth and other reasons had not been slaveholders, and had no particular sympathy with slavery, having found by personal experience that the presence of slave labor was disadvantageous to a large part of the white population. As a matter of fact, probably not more than one Southern family in four ever owned a slave.
The population required of a new State for admission to the Union in 1818 was 40,000. By the beginning of the Civil War the population of Illinois had increased to a million and three quarters. Obviously this change in little more than a generation represented only in small part the natural increase of the original settlers from Kentucky and Virginia. So rapidly, indeed, did the forces of progress act in Illinois that many of the old-timers packed up and moved on, as had happened during the previous generation among their parents, and Illinois in the following generation will be found strongly represented in the early migration to California, Kansas, Nebraska, and Colorado. To show how little slave-holding sentiment there was in the early Illinois population, in spite of its Southern origin, it is interesting to note that most of the Illinois contingent in Kansas were Free-State men whom the South regarded as enemies to its cause.
For every one of the old-timers who moved farther west, a dozen Yankees arrived along with many Pennsylvanians, while the Southern immigration almost entirely stopped, having been diverted to Texas or to territories beyond the Mississippi.
The people who left the slave-holding States in the decade prior to the Civil War were largely seeking free soil themselves. This movement of some of the best Nordic stock out of the South just before and at the beginning of the Civil War has not been given as much importance as it deserves. It was a factor in the weakening of the South and the strengthening of the North. While slavery was a curse in the opinion of many an owner of a great plantation, he was caught in the system and felt that he could not get away. The poor man, on the other hand, found conditions less and less to his liking and many of the more intelligent decided to get out of a country where they were obliged to compete with Negro slaves and were looked down upon by their white neighbors. In this way the lands along the Illinois Central Railway became a lode-stone for ambitious and dissatisfied farmers from Tennessee, Alabama, and even from Georgia. With the outbreak of hostilities this trickle became temporarily a torrent as political refugees who did not care to remain in a slave-holding republic at war with the American Union began to seek freer air.
The railroads developed a new specialty in transporting whole families with their furniture and agricultural implements to points in Illinois, Iowa, and Wisconsin, while steamers made their way up the Mississippi crowded with refugees and great numbers of Missourians crossed the river to Illinois with all their worldly goods. Many of the latter returned home after Missouri was cleared of secession, but their place was taken by new streams of Southerners released by the victories of Union armies and coming to join friends and relatives in southern and central Illinois.
The decline of leadership in the South after the war was not due entirely to the loss of its men on the battle-field. Although this was by far the principal factor, another important one was the flight from the South of many of those who were not in sympathy with the fire-eating politicians who had forced secession upon often unwilling communities.
Before this time, however, the streams of foreign-born which poured into the Mississippi Valley had already begun to influence the composition of the population of Illinois, so that even in 1850 one in four was of alien birth. The largest element was German, who formed farming communities, mainly in the northern and central part of the State. By 1860 there were 130,000 of them in Illinois, together with others who had also come from Pennsylvania.
Ireland sent the group of second importance, and the great internal improvements in this period were largely the product of their labor. As elsewhere the Irish showed little inclination for farming, which had proved so ruinous to them in Ireland, and they made a restless floating population in the large cities. In 1860 they represented four times as large a proportion of the population of Chicago as they did of the State as a whole.